During a fall from a height a peak force is induced within the cable of the lifeline, this force being defined as the maximum instant force developed in the direction of the cable under the effect of the impact applied at the time of fall arrest. To attenuate the size of this peak force it is known to equip the lifeline with an energy absorbing device to limit stresses transmitted to the anchor structure and to cushion the effect of the fall for the operator. A usual energy absorber comprises a static portion and a mobile portion secured together wherein the mobile portion is shifted in relation to the static portion in the event of a force higher than a force threshold value and actuates absorbing means. To prevent the absorbing means from coming into action under conditions of normal use, threshold triggering means are provided so that the absorbing means come into action on and after a force threshold value estimated and/or calibrated to correspond to the fall of an operator.
The static portion and the mobile portion each comprise fastening means arranged at one of their ends. The end of the mobile portion is connected to the cable of the lifeline on which a karabiner or equivalent means is attached connecting with the harness worn by the operator via a lanyard or strap. The cable of the lifeline is connected to an anchor point of the anchor structure. The end of the static portion is connected either directly or via another cable to another anchor point of the anchor structure. By “static portion” is meant a portion which, unlike the “mobile portion” does not move significantly in relation to the anchor points when the absorbing means are actuated.
Known energy absorbers have absorbing means which have recourse to compression or traction of elastic components, springs in particular. Other known energy absorbers have recourse to deformation e.g. plastic and/or rupture of materials when compressive or tensile demand is placed thereupon. Such absorbers are most often of single-use type.
The lifelines equipped with said energy absorbers are satisfactory to limit the consequences of a fall and to retain the operator. However, they do not allow transmission of data allowing detection that a fall has occurred. It is the objective of the present invention to obviate this disadvantage.